JP6618771B2 - Computer apparatus and simulation method for simulating in-body electrical conduction pattern at implantation site of implantable defibrillator - Google Patents

Description

  The present invention relates to a computer device for simulating a body electrical conduction mode when an implantable cardioverter defibrillator is operated at an implantation site of the implantable cardioverter defibrillator to be implanted inside a human body, and more particularly, to operate an implantable cardioverter defibrillator The present invention relates to a computer apparatus for simulating a conduction form from the internal body electrical conduction mode to the heart and measuring the degree of defibrillation effect and myocardial injury, and a simulation method using the computer apparatus.

  Implantable Cardioverter Defibrillator (ICD), which is implanted inside the human body, treats ventricular tachyarrhythmias such as ventricular tachycardia and ventricular fibrillation that cause sudden cardiac death It is an implantable medical device. Usually, the defibrillator body is placed in the front chest, and the lead connected to the body is placed in the right ventricle intravenously. The ICD senses the heart rate of the implanted human body, and when the heart rate exceeds a preset standard, direct current (electric shock) is applied between the body and the coil electrode installed on the lead. Defibrillation stops ventricular fibrillation and prevents sudden cardiac death.

  Defibrillation is performed by the electrical output exceeding the energy value (defibrillation threshold) that succeeds in defibrillation by the operation of ICD, but myocardial injury is caused by the high current, and life prognosis can be deteriorated The indwelling site of ICD for the purpose of suppressing myocardial injury has been studied (Non-patent Document 1).

  In recent years, a Subcutaneous Implantable Cardioverter Defibrillator (S-ICD, hereinafter abbreviated as S-ICD) has been developed that does not use a transvenous lead. Although treatment with ICD is also being performed, the defibrillation threshold of S-ICD is currently larger than that of ICD using conventional transvenous leads, and the possibility of myocardial damage has been pointed out, as with ICD (Non-Patent Document 2).

New Heartopics Vol.26 (JAPAN LIFELINE ARRHYTHMIA THERAPY REPORT) “Examination of device implantation site for the purpose of suppressing myocardial injury based on the effective body current conduction mode when implantable cardioverter defibrillator is activated” (Atsuto Noro), 2014.4 Computer Simulation of Defibrillations Using Subcutaneous Implantable Cardioverter Defibrillators, Xin Zhu, Mahito Noro and Kaoru Sugi, 2014.10

  Suppressing the output energy (defibrillation threshold) at the time of ICD operation may reduce the degree of myocardial damage and improve the prognosis of life. Based on the idea that the defibrillation threshold varies depending on the ICD implantation site, the present inventor calculates the defibrillation threshold and the degree of myocardial damage due to the electrical conduction pattern in the human body during ICD operation by computer simulation. I have been doing research.

  Therefore, an object of the present invention is to perform computer simulation of the ICD defibrillation threshold at the ICD implantation site and the degree of myocardial damage, thereby reducing defibrillation reliably with less damage to the heart. An object of the present invention is to provide a computer device and a simulation method that can determine an optimal implantation site that can be performed.

  In order to achieve the above object, a computer apparatus of the present invention is a computer apparatus for simulating an electrical conduction pattern in a body at the time of operation of an implantable defibrillator at an implantable site of the implantable defibrillator. Storage means for storing the data of the human body model in which the conductivity is set for each, and a plurality of main body placement sites where the implantable defibrillator main body can be placed in the human body model, and the implantable defibrillator main body With respect to all combinations of setting means for setting a plurality of lead indwelling sites where the connected leads can be indwelled, a plurality of main body indwelling sites, and a plurality of lead indwelling sites, a division according to the conductivity set in the human body model is performed. The value of a function that calculates the fibrillation threshold and the volume that is subjected to myocardial injury, and further includes the defibrillation threshold and the volume that is subject to myocardial injury that are obtained by calculation as variables A calculating means for calculating a combination of a predetermined value, and an outputting means for outputting the body indwelling site and lead placement site in a combination determined by the calculating means.

  Further, the simulation method of the present invention is a method for simulating in-body electrical conduction mode at the time of operation of the implantable defibrillator at the implantation site of the implantable defibrillator by a computer device. Storing the data of the human body model in which the rate is set in the computer device, a plurality of indwelling positions of the implantable defibrillator main body in the human body model, and the implantable defibrillator main body A step of setting a plurality of lead indwelling sites where a lead can be placed, and a defibrillation threshold corresponding to the conductivity set in the human body model for all combinations of a plurality of main body indwelling sites and a plurality of lead indwelling sites, and Calculate the volume subject to myocardial damage, and include the defibrillation threshold obtained by the calculation and the volume subject to myocardial damage as variables. The value of the function, characterized in that it comprises a step of outputting and obtaining a combination of a predetermined value, the body indwelling site and lead placement site in a combination determined by the calculating means.

  According to the computer apparatus and the simulation method of the present invention, the optimum implantation site of the implantable cardioverter defibrillator that most efficiently satisfies the two conditions of lowering the defibrillation threshold and reducing the occurrence area of the myocardial injury is determined. can do. In addition, the defibrillation with a lower defibrillation threshold enables the operation of a low-power defibrillator, thereby suppressing the occurrence of myocardial damage and further reducing the area where the myocardial damage occurs By placing a defibrillator in the center, it is possible to prevent the deterioration of life prognosis.

2 shows a configuration example of a computer apparatus according to an embodiment of the present invention. The whole flowchart of the simulation process in this Embodiment is shown. The flowchart of a human body model creation process is shown. The example of a human body model image is shown. An example of the ICD main body set on the human body model image data and the indwelling portion of the lead is shown. The example of an image of the current conduction path | route calculated | required by simulation calculation is shown. It is a flowchart of a success / failure part image display process of local defibrillation. It is an example of an image which visualized the success or failure site of local defibrillation by the processing of FIG. It is a flowchart of a myocardial injury occurrence site image display process. FIG. 10 is an image example in which the presence or absence of a myocardial injury occurrence site is visualized by the processing of FIG. 9. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention.

  FIG. 1 shows a configuration example of a computer apparatus according to an embodiment of the present invention. The computer apparatus is a general-purpose personal computer, and may be of any type such as a stationary type or a notebook type. The computer device has a hardware configuration of a general-purpose computer device, and a CPU 112, a ROM 113, a RAM 114, a network interface 115, an input device 116, a display device 117, and a storage device 118 are connected to the bus 111.

  The CPU 112 performs data processing or calculation and controls various components connected via the bus 111, and functions as setting means, calculation means, and output means. The ROM 113 stores a control procedure (computer program) of the CPU 112 in advance, and the computer device is activated when the CPU 112 executes the computer program. The storage device 118 is, for example, a hard disk storage device or an optical disk medium such as a CD-ROM, and stores a computer program for executing the simulation in the present embodiment. The computer program is copied to the RAM 114 and executed. . The CPU 112 executes the computer program to execute a simulation process in the present embodiment described later. The RAM 114 is used as a work memory for data input / output, transmission / reception, and temporary storage for control of each component.

  The network interface 115 is an interface for connecting to the Internet, which is a network. The input device 116 is a keyboard, a mouse, or the like, for example, and can perform various designations or inputs. The display device 117 is a display means such as a display. When printing out, the printer functions as a display device.

  Next, simulation processing according to this embodiment executed by the above-described computer apparatus will be described.

  FIG. 2 shows an overall flowchart of the simulation processing in the present embodiment. As a computer program for executing simulation processing, for example, SCIRun known as general-purpose simulation software can be used.

  First, data of a three-dimensional human body model of the patient is created from medical images such as CT images and MRT images of the patient's own human body (S100). The human body model includes the organ model included in the human body model, and semi-automatically (image processing + manual correction) or manually extracts a human body part such as a lung, heart, and bones, skin, blood vessels, etc. from a medical image. Thus, a human body model is created. The positions of organs and parts constituting the human body model are defined as three-dimensional coordinate values. The human body model may not be the whole body, and in the present invention, it may be a model of a part of the human body including the heart and the lungs near which the ICD is implanted.

  FIG. 3 shows a flowchart of the human body model creation process. First, a medical image (CT image or MRI image) is read (S101), lungs and bones are extracted using image values, and boundaries are set (S102). Further, fat, myocardium, heart lumen, and blood vessel are extracted using the image numerical values, and the boundaries are set (S103). The remaining tissue is set as a muscle (S104). Further, in order to obtain a calculation model for the finite element method described later, a mesh model of an organ including the heart is created (S105).

  FIG. 4 shows an example of an image of a human body model, in which the front surface of the human body is displayed, the skin is transparent, and the organs can be displayed in different colors. Is displayed in a different coloring from other parts.

  Returning to FIG. 2, parameters including conductivity (or resistance value) are set for the organs and parts in the created human body model (S110). By setting different conductivity for each organ or part, it is possible to simulate current conduction and voltage distribution from the ICD body to the lead during defibrillation.

  Then, the ICD main body and lead indwelling site (position) are set for the created human body model (S120). A coordinate area where the ICD body can be placed is defined, and the place where the ICD body can be placed is discretized to generate a plurality of coordinate positions where the ICD body can be placed. For the lead, the placement site is limited to a plurality of specific positions (RV, SVA, subcutaneous), and the specific positions are defined as coordinates. Also in the form in which two leads are placed, a specific position is defined with the placement site of each of the two leads as one placement pattern. One lead indwelling part is selected from a plurality of specific positions, and a simulation operation is executed for all the indwelling parts discretized in the indwellable coordinate area of the ICD main body for the lead indwelling part. As will be described later, all combinations of positions where the ICD main body position (detention site) and lead position (detention site) can be placed are sequentially selected, and simulation calculation processing is executed for all combinations.

  FIG. 5 shows an example of the ICD main body set on the image data of the human body model and the indwelling portion of the lead. FIG. 5A shows an example in which an ICD main body with one lead is placed in the front chest, FIG. 5B shows an example in which an ICD main body with two leads is placed in the front chest, and FIG. Shows an example in which the ICD body of one lead is placed in the axilla. Within the placeable coordinate area in the front chest or axilla, the placement site of the ICD body is defined in a discrete manner, and the lead placement site is also a plurality of placement sites within the ventricle including the number of leads. It is defined as a specific position.

  In FIG. 2, after setting the ICD main body and the indwelling portion of the lead, a simulation calculation is performed on the current conduction and voltage distribution during defibrillation by an algorithm of simulation software (S130). The simulation calculation is performed by, for example, a finite element method using a conjugate gradient and a Jacobi preconditioner, and a current conduction path and a voltage distribution are obtained by calculation. The simulation calculation is performed for a plurality of energy values step by step in a predetermined unit value (for example, 1 J or 0.5 J) within the output possible range of the output energy (J) of the ICD.

The defibrillation threshold (DFT) is expressed by the following equation.
DFT = 1 / 2CV ² (J)

  C is the capacitance of the ICD and is a constant of about 130 μF. V is the minimum voltage between the ICD body and the lead when the conditions for successful defibrillation are satisfied. The condition for successful defibrillation is when the region where the local potential space difference (voltage at 1 cm intervals) ΔV> 5 V / cm exceeds 90% of the myocardium in the voltage distribution obtained by simulation. The minimum energy value that succeeds in defibrillation is the defibrillation threshold. A region exceeding the local potential space difference ΔV> 30 V / cm is defined as causing myocardial injury.

  FIG. 6 shows an example of an image of the current conduction path obtained by the simulation calculation. FIG. 6 is a front image of a three-dimensional image, in which lines of electric force from the ICD main body to the leads are drawn. The current flows along the electric field lines, and the voltage distribution can be represented by an equipotential surface perpendicular to the electric field lines.

  The local potential space difference ΔV is calculated by numerical analysis of the simulation calculation result, and the defibrillation threshold (DFT) and the volume of the myocardial region where the myocardial injury occurs are obtained (S140). As described above, the myocardial region where the local potential space difference ΔV> 5 V / cm is a region where local defibrillation has been successful, and the other myocardial regions are regions where local defibrillation has failed. The myocardial region where the local potential space difference ΔV> 30 V / cm is a region where myocardial damage occurs, and the other myocardial regions are regions where no myocardial damage is caused.

  In the simulation calculation for multiple output energy values of ICD, defibrillation is performed with the minimum energy value when defibrillation is successful (when the region where the local potential space difference ΔV> 5 V / cm exceeds 90% of the myocardium) The threshold value (DFT) is determined, and the volume of the myocardial region that causes myocardial injury in that case is determined.

  Further, the volume of the myocardial region that causes myocardial damage is obtained by dividing the volume into important and non-important parts of the heart. In the heart, the part called the stimulus conduction system is a structure that transmits the heartbeat rhythm generated in the part called the sinoatrial node to the myocardium of the entire heart and makes it effective. When it occurs, it cannot conduct myocardial excitement. Therefore, it is considered that adjusting the placement location of the ICD in consideration of obstacles to the stimulus conduction system will lead to prevention of deterioration of the life prognosis. Each part is determined as an unimportant part. Sites constituting the stimulation conduction system include at least the sinoatrial node, the atrioventricular node, and the His bundle.

  In FIG. 2, after determining the defibrillation threshold (DFT) and the volume of the myocardial region (an important part and an unimportant part) that cause myocardial injury, the value of the optimum position function F (x, y, z) is obtained ( S150).

The optimum position function F (x, y, z) is defined by the following equation.
F (x, y, z) = J (x, y, z) + λ1d1 (x, y, z, J) + λ2d2 (x, y, z, J) (1)

  Where x, y, z is the position of the ICD body, J (x, y, z) is the energy value when defibrillation is successful, d1 is the volume at which the failure occurs in an important part of the heart, d2 is a volume in which a disorder occurs in an unimportant part of the heart, and λ1 and λ2 are weighting coefficients, and usually λ1> λ2 (λ1 + λ2 = 1). In the above equation (1), the coordinates (x, y, z) at which the value of the optimum position function F (x, y, z) is minimum is the optimum part of the ICD main body.

  In step S160, it is determined whether or not the simulation calculation has been performed for all the specific positions with respect to the lead indwelling site (S160). If there is a lead placement site (including the number of leads) that has not been simulated, the lead placement site setting is changed to the remaining placement site (S170), and the processing from steps S120 to S160 is repeated. .

  If there is no indwelling part of the lead that has not been simulated, simulation calculation has been performed for all combinations of the indwelling part of the ICD main body and the indwelling part of the lead. The position where the function F is minimized (the combination of the coordinates (x, y, z) of the ICD main body and the lead indwelling site (including the number of leads) in that case) is determined and output (S180). The output ICD body and lead placement site are the positions that most efficiently satisfy the two conditions of lowering the defibrillation threshold and reducing the myocardial injury occurrence area. A simple indwelling site can be obtained. The optimal placement site is output as an image display or numerical display.

  An image of the simulation calculation result at the optimal placement site of the ICD determined in S180 may be displayed. As an image display process for visualizing the simulation calculation result, for example, a process for displaying a region where local defibrillation is successful and a region where the defibrillation is failed, and a process for displaying a region where a myocardial disorder has occurred and a region where it does not occur are displayed in different colors Can be executed.

  FIG. 7 is a flowchart of the success / failure part image display process of local defibrillation. The mesh model of the heart part of the human body model and the simulation calculation results (voltage distribution and potential space difference data) for that part are read (S200), and whether the potential space difference ΔV for each mesh model is ΔV> 5V / cm When the determination is made (S201) and ΔV> 5 V / cm, a numerical value 1 is given to the unit center (S202). Otherwise, a numerical value 0 is given to the unit center (S203). Then, for example, the numerical value 1 is blue and the numerical value 0 is red, and the heart mesh model is displayed as an image (S204).

  FIG. 8 is an example of a voltage distribution image obtained by visualizing the success or failure of local defibrillation by the process of FIG. As shown in FIG. 8, local portions that have succeeded or failed in defibrillation can be visualized in a color-coded manner as a three-dimensional image so that they can be easily identified.

  FIG. 9 is a flowchart of myocardial injury occurrence site image display processing. The mesh model of the heart part of the human body model and the simulation calculation results (voltage distribution and potential space difference data) for that part are read (S300), and whether the potential space difference ΔV for each mesh model is ΔV> 30V / cm When the determination is made (S301) and ΔV> 30 V / cm, a numerical value 1 is given to the unit center (S302), otherwise a numerical value 0 is given to the unit center (S303). Then, for example, the numerical value 1 is red and the numerical value 0 is blue, and the heart mesh model is displayed as an image (S304).

  FIG. 10 is an example of a voltage distribution image in which the presence or absence of a myocardial injury occurrence site is visualized by the processing of FIG. As shown in FIG. 10, a site where a myocardial injury has occurred and a site where it does not occur can be visualized as a three-dimensional image in a color-coded manner so that it can be easily identified.

  The above image display, such as the success or failure position of local defibrillation and the occurrence position of myocardial injury, is not limited to the case of the optimal indwelling part of ICD. Processing is possible.

  The present embodiment has the following effects. That is, it is possible to determine the optimal implantation site of the ICD that most efficiently satisfies the two conditions of lowering the defibrillation threshold and reducing the occurrence area of the myocardial injury. Since an optimal ICD implantation site can be determined for each patient before the ICD implantation operation, a DFT test during the implantation operation becomes unnecessary. In addition, defibrillation with a lower defibrillation threshold enables ICD operation with low output, thereby suppressing the occurrence of myocardial injury and reducing the burden on the patient, as well as reducing the size and extending the life of the ICD. Further, by placing the ICD at a site (position) that makes the area where the myocardial injury occurs smaller, it is possible to prevent the deterioration of life prognosis.

  The present invention is not limited to the above-described embodiment, and there are design changes within a range that does not depart from the gist including various modifications and corrections that can be conceived by those having ordinary knowledge in the field of the present invention. Of course, it is included in the present invention.

  111: Bus, 112: CPU, 113: ROM, 114: RAM, 115: Network interface, 116: Input device, 117: Display device, 118: Storage device

Claims (6)

In a computer device for simulating the electrical conduction pattern in the body at the implantation site of the implantable defibrillator ,
Storage means for storing data of a human body model in which conductivity for each predetermined part is set;
Setting means for setting a plurality of main body indwelling sites of the implantable defibrillator body in the human body model, and a plurality of lead indwelling sites of a lead connected to the implantable defibrillator body; ,
For all combinations of the plurality of main body indwelling sites and the plurality of lead indwelling sites, calculate a defibrillation threshold value and a volume subject to myocardial injury according to the conductivity set in the human body model, A computing means for obtaining a combination in which a value of a function including the obtained defibrillation threshold and a volume subjected to myocardial injury as a variable is a predetermined value;
A computer apparatus comprising: the main body indwelling portion and the output indwelling portion in a combination obtained by the calculating means. The predetermined value is a minimum value of the function,
The function is
F (x, y, z) = J (x, y, z) + λ1d1 (x, y, z, J) + λ2d2 (x, y, z, J)
x, y, z: ICD body placement site, J (x, y, z): energy value when defibrillation is successful, d1: volume where damage occurs in critical parts of the heart, d2: non-heart rate Volume at which failure in the important part occurs, λ1 and λ2: weighting factors,
The computer apparatus according to claim 1, wherein:   The output means outputs an image so as to be able to discriminate between a cardiac local site where defibrillation is successful and a cardiac local site where defibrillation is not possible based on a calculation result by the calculation unit. A computer device according to claim 1.   4. The image output unit according to claim 1, wherein the output unit outputs an image so that a local part of the heart where a myocardial disorder occurs and a local part where the myocardial disorder does not occur can be distinguished based on a calculation result by the calculating unit. The computer apparatus in any one. In a method of simulating a body electrical conduction pattern at an implantation site of an implantable defibrillator by a computer device,
Storing data of a human body model in which conductivity for each predetermined part is set in a computer device;
Setting a plurality of main body indwelling sites of the implantable defibrillator body in the human body model, and a plurality of lead indwelling sites of a lead connected to the implantable defibrillator body; and
For all combinations of the plurality of main body indwelling sites and the plurality of lead indwelling sites, calculate a defibrillation threshold value and a volume subjected to myocardial injury according to the conductivity set in the human body model, and further, by calculation Obtaining a combination in which a value of a function including a determined defibrillation threshold and a volume subjected to myocardial injury as a variable is a predetermined value;
Simulation method characterized by comprising the steps of outputting said body indwelling site before Symbol set only combination of the lead placement site. A computer device that simulates the electrical conduction pattern in the body at the implantation site of the implantable defibrillator,
Storage means for storing data of a human body model in which conductivity for each predetermined part is set;
Setting means for setting a plurality of main body indwelling sites of the implantable defibrillator body in the human body model, and a plurality of lead indwelling sites of a lead connected to the implantable defibrillator body; ,
For all combinations of the plurality of main body indwelling sites and the plurality of lead indwelling sites, calculate a defibrillation threshold value and a volume subjected to myocardial injury according to the conductivity set in the human body model, and further, by calculation A computing means for obtaining a combination in which a value of a function including a calculated defibrillation threshold and a volume subjected to myocardial injury as a variable is a predetermined value;
A computer program for functioning as an output means for outputting the main body indwelling part and the lead indwelling part in the combination obtained by the arithmetic means.